Wiring EG4 18KPV to Combo Breaker/Meter Box (Grid Tied, Full Home Backup)

[zanydroid]

Technically you've deleted the feeder tap at that point. FWIW you can do a "low knowledge approach" and just tell draftsman creating your submission ready plans to delete things, and they'll tell you No if it's not a good idea. And the AHJ will tell you No if their plan checker doesn't like it. Though note typically draftsman will not sign it, and leave it to you to sign it. If you want someone other than you to sign it you pay for an engineer stamp.

You could brick the inverter for other reasons, like bad firmware update or power surge.

The compromise some people do is leave some spare cable and polaris connectors in place to manually bypass. This is safe with a modern combo main which de-energizes 99% of the panel when you flip the main, and is pretty entry level DIY electrical. You just need an appropriately rated torque driver.

 

[SurferJon]

Technically you've deleted the feeder tap at that point. FWIW you can do a "low knowledge approach" and just tell draftsman creating your submission ready plans to delete things, and they'll tell you No if it's not a good idea. And the AHJ will tell you No if their plan checker doesn't like it. Though note typically draftsman will not sign it, and leave it to you to sign it. If you want someone other than you to sign it you pay for an engineer stamp.

You could brick the inverter for other reasons, like bad firmware update or power surge.

The compromise some people do is leave some spare cable and polaris connectors in place to manually bypass. This is safe with a modern combo main which de-energizes 99% of the panel when you flip the main, and is pretty entry level DIY electrical. You just need an appropriately rated torque driver.

Thank you!

My question is more: if I'm deleting the manual transfer switch, aren't the wires going to the inverter grid ports and coming from the inverter load ports originating in the same place? From the "Feeder Taps" area in my diagram below?

Not sure if I'm fundamentally misunderstanding something

 

[jeff.lankford]

One more thing I still don't understand.

We said I don't really need the "200 Amp Feeder Tap Breaker." Let's also say I exclude the "Manual Transfer Switch." Let's say I don't care if the system goes down when the inverter fails in 15 years and I just don't have power for a few days.

By removing those two "boxes" from the diagram, isn't the load from the inverter going straight to the feeder tap, which is also where the wires are going to the inverter's grid?

View attachment 249183

If you do what you're suggesting, eliminating all those components, then you won't have a "feeder tap" at all. You will just have a feeder, routed through the inverter, with no alternate path to your interior 200 amp subpanel. Your exterior combo box and interior subpanel would not be wired directly together at all. If you did keep a conductor path between the two panels (where the feeder tap with manual transfer switch is on the diagram), then you are basically shorting the inverter's grid and load lugs together. I assume doing this would render the inverter's ATS useless.

As mentioned above, you may want to run the conductor path between the two panels, and have the Polaris taps in place, but leave things disconnected until needed for an emergency bypass if the inverter fails. Personally, I like the idea of having both the manual transfer switch and the PV fused disconnect in place in order to isolate the inverter from the system if needed. If your interior 200 amp subpanel includes a 200 amp main breaker, then I think you can eliminate the "feeder tap breaker" but you should keep everything else in the diagram.

I've been lurking here awhile... I'm planning an install with an 18Kpv and battery rack for a whole house backup. I've been studying this diagram for the past week and had the same questions as you. The manual transfer switch seemed redundant to me since the inverter has an ATS, until I learned from reading this forum that these two switches work together to take the inverter out of the circuit.

 

[SurferJon]

Hmm, been thinking.

Do I even have to delete my old 100 amp panel or move its wires to the new panel?

Can I just do this: new 200 amp CSED -> its 200 amp breaker -> 18kpv grid ports, then 18kpv load ports -> my old 100 amp panel with all my house's breakers? Thus acting as a "critical loads" panel that has full home backup and grid-pass through?

And if I can do that, should I? Or would it be better for future-proofing and long-term quality to just do the new 200 amp CSED with a brand new subpanel inside the house, thus moving/extending the wires to it, and getting fresh new breakers?

I'll be living in this house for the rest of my life (60+ years hopefully). So I just want to do what's best for the long-term.

EDIT: And would this mean that anything upstream from the inverter in the main 200 amp panel wouldn't be powered by the inverter, meaning that when net metering ends in 20 years, everything in that box will have to be powered by the utility company instead of my solar setup?

 

[jeff.lankford]

Thank you!

My question is more: if I'm deleting the manual transfer switch, aren't the wires going to the inverter grid ports and coming from the inverter load ports originating in the same place? From the "Feeder Taps" area in my diagram below?

Not sure if I'm fundamentally misunderstanding something

View attachment 249194

I've been thinking about this picture some more. Just don't do this, for several reasons...

1. I already mentioned the ATS above. If you short/bypass the ATS, then during a power outage the inverter output is going to energize the line conductors unless you manually throw the main service disconnect during each outage. This is a common mistake of people operating a backup generator by back-feeding their main panel with the generator. It puts line workers at risk during the outage, and they may try to track you down in order to locate the rogue power source.
2. Tying the inverter output to the grid input will bypass the sell-back settings of the unit. During normal operation the inverter will backfeed the grid regardless of the sell-back settings, presumably up to the limit of its power output, and it will drain the battery bank in the process.
3. Doing this will also cause the inverter to attempt to charge the battery bank using AC output from the inverter. Creating this battery charging loop is a common problem in RV systems when people power their RV by connecting their inverter output to the NEMA30 or NEMA50 input to the camper without remembering to disable the converter.

Also, I believe now that if you omit the disconnect switches (the transfer switch and the PV fused disconnect) you will be violating NEC code. These physical disconnect means are required by NEC. If you install the 18Kpv outside, then the grid and load circuit breakers in the inverter may serve this purpose. But they will need to be clearly labeled as emergency disconnect, and you need to ensure the inverter cable box cover can never be locked. If the inverter is installed indoors, then the outdoor physical switches are required. The RSD button alone will not suffice. The RSD operation is a software function, and as a software engineer I can assure you that no software is 100% failsafe, including NASA and utility-grade software. If the RSD fails, then the physical disconnect is needed. Note that the NEC requires both the RSD function AND the physical disconnect switches.

FYI for everyone, the manual for the 12Kpv has some improvements over the 18Kpv manual and it is useful to refer to it even if you are installing the 18Kpv. They are virtually the same device and the manuals and diagrams are similar. The 12Kpv wiring diagram improvements include better annotations and, more importantly, they include citations to the relevant NEC code sections for each component on the diagram. Also, in case you're unaware you can access the NEC online for free - you don't need to buy a copy.

 

[jeff.lankford]

Hmm, been thinking.

Do I even have to delete my old 100 amp panel or move its wires to the new panel?

Can I just do this: new 200 amp CSED -> its 200 amp breaker -> 18kpv grid ports, then 18kpv load ports -> my old 100 amp panel with all my house's breakers? Thus acting as a "critical loads" panel that has full home backup and grid-pass through?

And if I can do that, should I? Or would it be better for future-proofing and long-term quality to just do the new 200 amp CSED with a brand new subpanel inside the house, thus moving/extending the wires to it, and getting fresh new breakers?

I'll be living in this house for the rest of my life (60+ years hopefully). So I just want to do what's best for the long-term.

EDIT: And would this mean that anything upstream from the inverter in the main 200 amp panel wouldn't be powered by the inverter, meaning that when net metering ends in 20 years, everything in that box will have to be powered by the utility company instead of my solar setup?

I can't think of a reason this wouldn't work, as long as the old 100 amp panel still contains a 100 amp main breaker to protect its smaller bus. But you will presumably be unmounting and moving that old panel with all of this, so if it were me I'd go ahead and install a newer 200 amp subpanel for future-proofing instead of re-mounting the old panel. At the very least, when wiring in the inverter I would use a wire size rated for 200 amp so at least that part of the install is future proof for swapping out to a larger panel later.

 

[SurferJon]

I can't think of a reason this wouldn't work, as long as the old 100 amp panel still contains a 100 amp main breaker to protect its smaller bus. But you will presumably be unmounting and moving that old panel with all of this, so if it were me I'd go ahead and install a newer 200 amp subpanel for future-proofing instead of re-mounting the old panel. At the very least, when wiring in the inverter I would use a wire size rated for 200 amp so at least that part of the install is future proof for swapping out to a larger panel later.

If I don't need to, I wouldn't be unmounting the old 100 amp panel or moving it. It's old and encased in mesh stucco. I'm assuming my electrician would just run wire from the 200 amp panel to it, which I would later intercept with the inverter's load. I broke open the stucco below the panel a while ago, so it's easy to run wire up to it.

Also, am I able to run another subpanel downstream from the inverter? As in, connect two 100 amp panels to it? The old one and another one in the future if I need more circuits backed up?

 

[jeff.lankford]

If I don't need to, I wouldn't be unmounting the old 100 amp panel or moving it. It's old and encased in mesh stucco. I'm assuming my electrician would just run wire from the 200 amp panel to it, which I would later intercept with the inverter's load. I broke open the stucco below the panel a while ago, so it's easy to run wire up to it.

Also, am I able to run another subpanel downstream from the inverter? As in, connect two 100 amp panels to it? The old one and another one in the future if I need more circuits backed up?

So you would leave the existing panel in place and move your service entrance to the mounting location for the new combo panel, i.e. move the mast head and conduit, or underground conduit, etc.? This sounds like a lot of trouble to create a weird solution (an entire new unused main panel that you will bypass). I'm wondering about going back to the original plan of just replacing old panel with new and figuring out the best connections for it. I looked at the new panel link and I see that it is "solar ready". There has got to be a rational way to use this box with the inverter. I was curious what "solar ready" means, and I find this in the panel description:
"
- Solar-ready for new or future installations with provisions for field-installed CT's on line bus
- Accepts solar ready sub-feed lug kit SR69064A for solar connections ahead of the main breaker (sold separately)
"
So the concern about where to place the CTs is covered by this panel. And there is a provision to pull the feeder tap off the panel with that optional lug kit. It sure looks like there is a more simple and elegant solution for what you are trying to do here, using only one panel.

 

[SurferJon]

The bus bars in CSEDs go directly from the 200 amp breaker to the load center. You can't disconnect that connection to put the inverter's load wires in-between.

 

[SurferJon]

The city is now telling me an AC disconnect is required before my inverter. As in, Meter CSED -> its 200 amp breaker -> AC disconnect -> inverter -> subpanel with all the house's loads.

Isn't an AC disconnect redundant when you can just flip the 200 amp breaker to turn off the inverter? Everything is after the inverter anyway.

 

[BentleyJ]

Yes, but the code treats an inverter the same as piece of equipment for example a roof top package unit would need a disconnect on or near the unit on the roof.

 

[SurferJon]

I wonder if I can remove it after the inspector comes. Seems completely unnecessary to have it.

 

[jeff.lankford]

I wonder if I can remove it after the inspector comes. Seems completely unnecessary to have it.

I still don't understand why you are so intent on omitting the disconnect / bypass switches from EG4's recommended design.
Did you wind up omitting the manual transfer switch from your design as you were intending?

FWIW, I think you are making a big mistake by not giving yourself the ability to take the inverter out of service, bypass and isolate the thing using the MTS and AC disconnect switches, and restore grid power to your house.

I am at the tail end of getting my system installed now. One 18Kpv and four LL-S rack batteries in an EG4 rack. No PV yet - this is only a battery backup system initially. I have had a number of issues so far getting the system up and running, getting the inverter coordinating with the batteries, etc. At the current stage, I have the system switched in to my house, and things are not working right. Although the 18Kpv is reporting it has a good grid connection, it is NOT passing through grid power. It is currently draining the battery bank to power the house and using 0 watts from the grid. All settings look good to operate only as backup as intended. If I don't get this figured out soon, I will need to isolate the inverter and switch grid power back to my house with the MTS before it kills the batteries.

I am certain this is just a wrong setting that we will figure out. My point here is that it would be an enormous PITA to switch my house back to grid if the two switches in question were not included. Any problems with the inverter in the future - same thing. I would not want to be outside in the dark and rain trying to move hot wires around to get power back because the inverter has quit in the middle of the night. Be aware that the inverter must be up and running in order to pass through grid power to your house. It looks like the inverter must boot up and software must throw the bypass relays in order for grid power to get to your house, so don't assume that if there's a fault you will still have power getting to your house.

 

[SurferJon]

So I am going to start installing the rails on the roof next week and then the solar panels a week or two later. Beyond the panels and racking I haven't bought any other equipment yet, including the inverter, wiring, or batteries. I'm waiting until Black Friday.

After I'm done on the roof, the electrician is coming out to relocate the service mast next to the back door (per Edison's meter spot location). He's going to install this way too large 200 amp main panel next to the back door because it's the only flush unit we could find. (I wanted a flush unit because I don't want a big ol' box sticking out of the wall when you come out of the back door.) We won't be using any of the breaker spaces inside of it, so it's kind of a waste of space. Then he's going to run that to the 18kpv inside the house and then to a new 200 amp subpanel with all the house's loads.

This is my upcoming setup that's been approved by the city:



However, I just heard about the GridBOSS. I'm wondering if it would allow for a cleaner installation.

I'm wondering if I can do a flush 200 amp meter socket next to the back door (like this small one) that runs less than 5 feet to the Gridboss inside the house's utility closet. Since the GridBOSS has a service disconnect, would that eliminate the need for a combo meter box outside the back door with a 200 amp disconnect? And if so, could the GridBOSS be installed inside the house, or would that be bad because firefighters wouldn't be able to turn off the power? And then of course the GridBOSS would connect to the FlexBOSS21 and the 200 amp subpanel inside the house.

Basically my goal is to figure out a way to have less boxes next to my back door, or at least make them flush. I want to put as much as possible in the utility closet inside the house.

 

[jeff.lankford]

Doesn't your local code require a main disconnect located outside the structure? I doubt you can pass an inspection if you eliminate that from your design.

BTW, why use 4/0 copper for this when only 2/0 is required for 200A?

 

[fatanu]

I'd like to follow up on how you concluded your setup. I have to do similar setup, but in my case, I have an existing on-grid solar that I am trying to convert to hybrid. The wiring connection recommended is the whole home backup using feeder tap. Did you eventually user feeder tap and pv interactive 2-pole fused disconnect? Please what did you use to make the wiring connection work?

 

[jeff.lankford]

I'd like to follow up on how you concluded your setup. I have to do similar setup, but in my case, I have an existing on-grid solar that I am trying to convert to hybrid. The wiring connection recommended is the whole home backup using feeder tap. Did you eventually user feeder tap and pv interactive 2-pole fused disconnect? Please what did you use to make the wiring connection work?

As for myself, there is no separate box/device for the "feeder tap." My tap is made inside the manual transfer switch - instead of using Polaris taps I swapped out the single lugs for the grid supply to the switch and replaced them with dual lugs. The dual lugs give me the tap connection to route to the inverter. For the "pv interactive 2-pole fused disconnect" I used a smaller and much cheaper 200A service disconnect box instead of the fused knife switches most people seem to find:

https://www.lowes.com/pd/Square-D-200-Amp-Main-Breaker-Load-Center/3471297

I did NOT include a separate feeder tap breaker in my design. The output from my meter/main goes directly to the dual lugs in the manual transfer switch.

I would strongly suggest you keep the manual transfer switch and the inverter disconnect switch in your design so you can isolate the inverter for service and keep grid power to your house.

 

[fatanu]

@jeff.lankford Thank you. Did you do all this installation yourself? I'm struggling to get electrician to help me out. They back out once they hear solar and said they don't do any electrical work related to solar. If you do it, I'd appreciate your help and guidance. I can directly provide you more details. In the meantime, can you please provide recommendation and links of which feeder tap, feeder tap breaker, manual transfer switch to get.

Thank you.

 

[jeff.lankford]

@jeff.lankford Thank you. Did you do all this installation yourself? I'm struggling to get electrician to help me out. They back out once they hear solar and said they don't do any electrical work related to solar. If you do it, I'd appreciate your help and guidance. I can directly provide you more details. In the meantime, can you please provide recommendation and links of which feeder tap, feeder tap breaker, manual transfer switch to get.

Thank you.

Yes, I pulled a permit and did this myself. My work passed final inspection, FWIW.

I used this for the manual transfer switch:

GE 200 Amp 240-Volt Non-Fused Emergency Power Transfer Switch TC10324R - The Home Depot

Run your backup generator with this UL recognized GE Non-Fused Emergency Power Transfer Switch. Features metal construction.

www.homedepot.com

And this for the "PV Interactive System Disconnect":

https://www.lowes.com/pd/Square-D-200-Amp-Main-Breaker-Load-Center/3471297

As stated above, I did not use a feeder tap breaker, and I do not have a feeder tap enclosure. I made my tap inside the manual transfer switch enclosure using dual lugs instead of Polaris taps.

I'm referencing the EG4 18Kpv diagram "Whole Home Backup using a Feeder Tap", but in my case there is a direct connection from my Main Service Breaker to the Manual Transfer Switch. The grid input to the MTS lands on dual lugs, and that serves as a tap connection which runs to the input of the PV System Disconnect. Everything else about the system is the same as the diagram shows.
My entire house service runs through the inverter, so I used 2/0 copper for all the AC cabling.

 

[jeff.lankford]

@fatanu

Here is a simplified diagram. I had an existing meter / main outside and a service entrance cable running to an inside main panel. I did not change the existing boxes and did not pull a new service entrance cable. Instead I used Polaris blocks to make a splice inside the main disconnect enclosure and extend the cable running to the main panel another three feet over to the MTS.

 

[fatanu]

Thanks @jeff.lankford You are really inspiring me that its something I can do myself. In my case, i have an existing on-grid solar system. From the guide, the cable from the current PV disconnect goes into the inverter gen ports. See my current setup. It looks like my main service breaker has 200amp breaker so i don't need the feeder tap breaker.

 

[jeff.lankford]

@fatanu

Are you intending to route your entire house service through the 18Kpv and not create a new critical loads panel? If so, and if you plan to install the 18Kpv outdoors, I think your install can be exactly like what I did.

From the photos, I assume your main service entrance cable exits the back of your meter/main into the wall and runs to the main breaker panel indoors, as does mine. You’ll probably want to relocate your existing PV disconnect to make room for the MTS adjacent to the meter/main. Where you mount the inverter will be dictated by where you place the batteries, to keep your DC cables as short as possible. For me, the inverter is about 25 feet away from the MTS due to where I installed the battery rack indoors. So I have a pretty long AC cable run back and forth between the MTS and the inverter & its disconnect.

It looks like your main panel is a main lug and not a main breaker. Without a main breaker at the panel, the 200A load breaker in the 18Kpv will be the only overcurrent protection on your new cabling… you might want to check with your county permit office to make sure this will be acceptable, if you intend to pull a permit.

Here’s some shots of my install. The lugs inside the MTS are easily replaced with the dual lugs for the tap. One odd thing about the GE MTS – the enclosure has no equipment ground lug to ground the box. The neutral lug block is isolated from the box, so the ground shouldn’t go there. I had to drill and tap a hole to add the ground lug you see in the MTS photo. There are Polaris blocks inside the main disconnect which are splices, not taps. That’s the method I used to extend the main panel service entrance cable over to the MTS load connections.

My grid service is only 150A, but I still used 2/0 copper for everything I added because of the 200A load breaker in the 18Kpv and because of the relatively long cable run I had to make back and forth between the MTS and inverter. Smaller cable would not be properly overcurrent protected by the 200A load breaker. I found the warning labels on Amazon. They are the exact wording and format required in the NEC code sections for PV and ESS systems.

 

[jeff.lankford]

@fatanu

Regarding my comment about your main breaker panel...
You may want to review the rules for feeder taps. I found this video to be very helpful:

You're allowed to make a feeder tap as long as the tap wires are protected at their downstream end by a suitably sized circuit breaker. I'm not sure if the 18Kpv load breaker satisfies the requirement. In my case it would not because the existing wiring to my main panel is only sized for 150A. My inside main panel includes a 150A main breaker, so that satisfies this tap rule. You might need to add the "feeder tap breaker" from the EG4 diagram into your design. If so, you could use the same device as I've used for the PV System Disconnect.

If your main panel has the option of adding a main breaker, then that would likely be a much simpler and cheaper option than adding the feeder tap breaker. You could then stick with my method of making the tap inside the MTS at the dual lugs I added.

 

[fatanu]

@jeff.lankford Thanks for the information. I intend to route all my house through the 18Kpv inverter. The Inverter would be placed on the wall (inside my garage) behind where my main service breaker is,. I plan to place it in the spot between my current PV AC disconnect and my main service/meter, that way I can easily take the cable coming from my current PV AC disconnect to the inverter gen port. I intend to place the feeder tap and the new PV disconnect between where my current PV ac disconnect and my main service/meter. I know its a tiny space but I want to pass both the cables from the current AC disconnect and the new PV disconnect into a hole through the wall to get to the inverter. The manual switch will be beside my main breaker panel but I will need to run the cable to where my inverter, which is about 10 feet.

So a question; does the feeder tap needs to connect to the manual transfer switch? the diagram only shows one line connecting the feeder tap and manual switch, so I am not sure if that mean cable connection. If that is the case, then I will most likely place the manual transfer switch beside the inverter so it can also get the cable through the same hole from the feeder tap.

I am amateur in electrical connection, but I will definitely share your connection details to an electrician to break it down on how it mean to my existing setup, but what I just explained is based on my understanding of the diagram.

The feeder tap breaker......do i need this...in my main service breaker, does it not contain a 200amp breaker? I will try and draw how I understand my connection should be and share it here later today. Thanks

 

[fatanu]

@jeff.lankford some questions that came to my mind:
1) when all the connections are completed, the only power grid cable that goes to the main breaker panel should come from the manual transfer switch. If this is yes, the existing power grid connection that comes from the main server breaker will be removed?
2) If the existing power grid cable needs to be removed, instead of removing it, can I tap it to connect to the Manual transfer switch, that way I avoid having to do anything in the main breaker panel? I'm just trying to avoid touching existing connection and just use existing cables/connections as much as possible. But, the question would be if the cable they use for it will work with the manual transfer switch.

Please let me know, thanks!